Browsing by Author "Le Maitre, David C."

Now showing 1 - 4 of 4
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    National-scale strategic approaches for managing introduced plants : insights from Australian acacias in South Africa
    (Blackwell Publishing, 2011) Van Wilgen, Brian W.; Dyer, Colin; Hoffmann, John H.; Ivey, Philip; Le Maitre, David C.; Moore, Joslin L.; Richardson, David M.; Rouget, Mathieu; Wannenburgh, Andrew; Wilson, John R. U.
    Aim: A range of approaches and philosophies underpin national-level strategies for managing invasive alien plants. This study presents a strategy for the management of taxa that both have value and do harm. Location: South Africa. Methods: Insights were derived from examining Australian Acacia species in South Africa (c. 70 species introduced, mostly > 150 years ago; some have commercial and other values; 14 species are invasive, causing substantial ecological and economic damage). We consider options for combining available tactics and management practices. We defined (1) categories of species based on invaded area (a surrogate for impact) and the value of benefits generated and (2) management regions based on habitat suitability and degree of invasion. For each category and region, we identified strategic goals and proposed the combinations of management practices to move the system in the desired direction. Results: We identified six strategic goals that in combination would apply to eight species categories. We further identified 14 management practices that could be strategically combined to achieve these goals for each category in five discrete regions. When used in appropriate combinations, the prospect of achieving the strategic goal will be maximized. As the outcomes of management cannot be accurately predicted, management must be adaptive, requiring continuous monitoring and assessment, and realignment of goals if necessary. Main conclusions: Invasive Australian Acacia species in South Africa continue to spread and cause undesirable impacts, despite a considerable investment into management. This is because the various practices have historically been uncoordinated in what can be best described as a strategy of hope. Our proposed strategy offers the best possible chance of achieving goals, and it is thefirst to address invasive alien species that have both positive value and negative impacts.
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    Natural hazards in a changing world : a case for ecosystem-based management
    (PLoS, 2014) Nel, Jeanne L.; Le Maitre, David C.; Nel, Deon C.; Reyers, Belinda; Archibald, Sally; Van Wilgen, Brian W.; Forsyth, Greg G.; Theron, Andre K.; O’Farrell, Patrick J.; Kahinda, Jean-Marc Mwenge; Engelbrecht, Francois A.; Kapangaziwiri, Evison; Van Niekerk, Lara; Barwell, Laurie
    Communities worldwide are increasingly affected by natural hazards such as floods, droughts, wildfires and storm-waves. However, the causes of these increases remain underexplored, often attributed to climate changes or changes in the patterns of human exposure. This paper aims to quantify the effect of climate change, as well as land cover change, on a suite of natural hazards. Changes to four natural hazards (floods, droughts, wildfires and storm-waves) were investigated through scenario-based models using land cover and climate change drivers as inputs. Findings showed that human-induced land cover changes are likely to increase natural hazards, in some cases quite substantially. Of the drivers explored, the uncontrolled spread of invasive alien trees was estimated to halve the monthly flows experienced during extremely dry periods, and also to double fire intensities. Changes to plantation forestry management shifted the 1∶100 year flood event to a 1∶80 year return period in the most extreme scenario. Severe 1∶100 year storm-waves were estimated to occur on an annual basis with only modest human-induced coastal hardening, predominantly from removal of coastal foredunes and infrastructure development. This study suggests that through appropriate land use management (e.g. clearing invasive alien trees, re-vegetating clear-felled forests, and restoring coastal foredunes), it would be possible to reduce the impacts of natural hazards to a large degree. It also highlights the value of intact and well-managed landscapes and their role in reducing the probabilities and impacts of extreme climate events.
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    Prosopis : a global assessment of the biogeography, benefits, impacts and management of one of the world’s worst woody invasive plant taxa
    (Oxford University Press on behalf of the Annals of Botany Company, 2014) Shackleton, Ross T.; Le Maitre, David C.; Pasiecznik, Nick M.; Richardson, David M.; Dukes, Jeffrey S.
    Invasive species cause ecological, economic and social impacts and are key drivers of global change. This is the case for the genus Prosopis (mesquite; Fabaceae) where several taxa are among the world's most damaging invasive species. Many contentious issues (‘conflicts of interest’) surround these taxa, and management interventions have not yet sustainably reduced the negative impacts. There is an urgent need to better understand the factors that drive invasions and shape management actions, and to compare the effectiveness of different management approaches. This paper presents a global review of Prosopis, focusing on its distribution, impacts, benefits and approaches to management. Prosopis was found to occur in a 129 countries globally and many more countries are climatically suitable. All areas with naturalized or invasive Prosopis species at present are suitable for more taxa and many Asian and Mediterranean countries with no records of Prosopis are bioclimatically suitable. Several Prosopis species have substantial impacts on biodiversity, ecosystem services, and local and regional economies in their native and even more so in their invasive ranges; others provide multiple benefits to local communities. Management efforts are underway in only a small part of the invaded range. Countries where more research has been done are more likely to implement formal management than those where little published research is available. Management strategies differ among countries; developed nations use mainly mechanical and chemical control whereas developing nations tend to apply control through utilization approaches. A range of countries are also using biological control. Key gaps in knowledge and promising options for management are highlighted.
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    Use of non-timber forest products from invasive alien Prosopis species (mesquite) and native trees in South Africa : implications for management
    (Springer, 2015) Shackleton, Ross T.; Le Maitre, David C.; Van Wilgen, Brian W.; Richardson, David M.
    Background: Prosopis species have been introduced to many areas outside their native range to provide benefits to local communities. Several Prosopis species and their hybrids (hereafter “mesquite”) have, however, become naturalised and invasive and now generate substantial costs. Management options are limited because of the complex conflicts of interest regarding benefits and costs. Management policies and strategies must take account of such conflicts, but further insights are needed on the dimensions of uses and impacts before such information can be usefully applied. Current policy in South Africa allows for the growth and use of mesquite in one province, but not in others where its control is mandatory. We report on a study to quantify the direct use and perceptions of non-timber forest products (NTFPs) from mesquite and native trees in South Africa. Methods: Semi-structures household interviews were conducted with various stakeholder groups to identify what tree products are used, to ascertain amounts used as well as to gauge perceptions of natural resource use between different tree species and use over time. Results: The direct household use value of native trees was higher than that of mesquite, and local stakeholders attached greater value to products from native trees than from mesquite. Therefore, native trees are and will still be preferentially harvested, and mesquite is unlikely to offer protection to native species by providing an alternative source of products. Mesquite pods do, however, provide valuable additional resources (fodder and medicinal products). The use of both native trees and mesquite is decreasing as the incomes of poorer households rise and as alternative energy sources become available. The benefits and reliance on mesquite are not as high as previously assumed and the impacts from mesquite invasions create large problems for local communities. Conclusion: This study provides further evidence that the impacts of mesquite exceed the benefits, lending support for a policy to reduce negative impacts.